Over the years a variety of power or energy sources operating off of heat derived from the oxidation of metallic lithium have been proposed. See, for example, U.S. Letters Pat. No. 3,329,957 issued July 4, 1967 to Rose. In such a system, water and lithium are reacted to produce lithium hydroxide, hydrogen and steam. Elsewhere in the system, the hydrogen, generated by the reaction between lithium and water is combined with oxygen to provide additional steam. The steam is then utilized to drive a turbine or the like to provide a source of power.
More recently, somewhat similar systems have been proposed wherein metallic lithium, in the solid phase, is placed within an oxidation chamber of a boiler. When power is desired, the lithium is melted and oxidized with sulfur hexafluoride. The resulting heat vaporizes a working fluid, typically water, in a working fluid chamber in heat exchange relation with the oxidation chamber of the boiler. Again, a turbine may be driven by the working fluid.
While such a system is effective, it is not without its drawbacks. Typically, the system start is initiated by firing a thermal starting device which includes aluminum potassium perchlorate. The intention is to heat the thermal mass of the boiler and the lithium fuel therein to operating temperature and to this end, the aluminum potassium perchlorate generates extremely high temperatures, typically in the range of 5400.degree.-8500.degree. F. Substantial pressures may be generated during the ignition of the aluminum potassium perchlorate requiring high strength of the boiler structure. Furthermore, the aluminum potassium perchlorate, should it contact boiler surfaces or sulfur hexafluoride injection nozzles, can burn through the same resulting in system damage.
In my above referenced pending patent application, the details of which are herein incorporated by reference, there is described a power source which primarily operates as a result of heat generated by a lithium-sulphur hexafluoride reaction which avoids the difficulties occasioned by the use of aluminum potassium perchlorate or other like starters. In particular, lithium pellets are encapsulated within a predominently fluorine substituted polymeric material. Such encapsulated pellets are then disposed within the boiler of the power source. A relatively low temperature thermal starting device can be utilized to initiate a reaction between the lithium metal and the polymeric coating simply by raising the temperature of a relatively few of the pellets to approximately the melting point of lithium, namely, 357.degree. F. This initial reaction heats the remainder of the mass while generating lithium fluoride and lithium-carbon compounds. Sulfur hexafluoride, after the initial reaction has been initiated, is then admitted to the boiler, generally in a controlled fashion, to maintain a reaction with the lithium, again generating lithium fluoride and in addition, lithium sulfide.
The system works very well for its intended purpose and avoids the problems heretofore associated with power sources utilizing a lithium-sulphur hexafluoride reaction to provide heat. However, the method of encapsulating the lithium pellets described in my co-pending application requires the transfer of lithium pellets from a coating apparatus to the boiler after the pellets have been encapsulated and this step desirably would be eliminated.
The present invention is directed to accomplishing just that.